1. Field of the Invention
The present invention relates to a technical field of image processing and, more particularly, to a detecting system and method of compression-related noise levels.
2. Description of Related Art
With the advance of digital compression technologies, more and more current TV images are digitally compressed before storage or transmission, and decompressed before play. Such a way can increase the capacity of transmission data and reduce the analog noises. A typical digital compression is an MPEG compression. For the reconstructed images that are distorted after the MPEG compression, some digital defects become obvious when the compression rate is high. In addition, due to the different quantitative levels in compression, certain noises may be produced. For example, when a high quantification is applied to a block-based compression, the boundaries between the blocks may present discontinuous, and the blocking artifacts may be produced on a display image.
To overcome the aforementioned problem, a post-processing technique such as de-blocking or de-ringing at the decompression side is typically applied. Such a post-processing basically assumes that the boundaries between the blocks are known. Accordingly, the correlation parameters obtained by analyzing a compressed image are used to detect the possible blocking artifacts for further performing the post-processing in different levels respectively. In the U.S. Pat. No. 6,611,295, it discloses an MPEG block detection that is applied at the display side, without needing the information at the decompression side. At first, the brightness gradient information of an image is found. Next, the block locations possibly presented are analyzed and counted. Thus, the boundary locations of the original compressed blocks are detected. However, when the compression rate is increased to thus reduce the image quality, the edges with higher image space frequencies typically present ringing. Blocking presents when a wide range of motion occurs. Generally, only analyzing the image content, without using the compression-related data, is hard to properly separate the compressed noises from the original images completely. For producing a preferred estimation index, a span of measure is used in reference to a coincidence of the degree of compressing a same signal source. However, since blocking presents only when the wide range of motion occurs, the noises caused by compressing the images are easily underestimated for a less motion scene.
Therefore, it is desirable to provide an improved detecting method and system to mitigate and/or obviate the aforementioned problems.